Is the problem you are seeing like the one I reported w.r.t.
unionfs in kern/8209?

					Gary D. Duzan


In Message <199910010729.JAA00317@jdolecek.per4mance.cz> ,
   Jaromir Dolecek <dolecek@ics.muni.cz> wrote:

=>The current order of unmounting in vfs_unmountall() is that 
=>volumes are unmounted in opposite order they were mounted, i.e.
=>leaves are umounted first. While playing with fs staff, I got
=>many times to the sitation when this order is not very comfortable.
=>My test volume is normally the last one mounted and when
=>it's locked up, the kernel never gets to umount other volumes.
=>
=>It would be cool if the order in which vfs_umountall() umounts
=>volumes would be switchable. I though about some simple vfs.umountall_lifo
=>sysctl flag, default on. Do you think such thing would be usable ?
=>
=>Jaromir
=>-- 
=>Jaromir Dolecek <jdolecek@NetBSD.org>      http://www.ics.muni.cz/~dolecek/
=>"The only way how to get rid temptation is to yield to it." -- Oscar Wilde